1. Field of the Invention
The present invention relates to a hose, and more particularly, a low noise hose used in an intake air system of an internal combustion engine.
2. Description of Related Art
Conventional low noise hoses are described in EP Patent No. 0,318,636 B1 and German Patent No. 2,749,665.
FIG. 14 shows such a conventional low noise hose 51 that is of multi-layered construction, consisting of spiral wire 52 used for an anti-shrinkage member, a synthetic resin net 53, a cylindrical sound absorption member 54 and a synthetic resin skin 55, sequentially from inside, and side members 56 engaged on both sides of the low noise hose 51. The sound absorption member 54 is made of soft foam material of synthetic resin, and the cell of the foam is connected to the next one. The hose internal noise can be reduced by the sound absorption material 54.
However, since the synthetic resin skin 55 is a film having a thickness less than 0.1 mm, internal noise passing through the sound absorption material 54 is leaked to the external portion of the hose without being absorbed in the synthetic resin skin 55. Further, since the synthetic resin skin 55 is thin and easily damaged by heat, oil, or gas or the like, there are some problems regarding durability when used in severe circumstances such as in an engine room. The synthetic resin skin 55 is used since the low noise hose 51 can be assembled freely and can be shrunk to absorb the pulsation of intake air. If thick synthetic resin skin 55 is used, the silencing effect can be increased, however, the low noise hose 51 can not be assembled freely, and can not absorb the pulsation of intake air.